1. Field of the Invention
This invention relates to microwave ovens and in particular to means for providing air flow through microwave ovens.
2. Description of the Prior Art
In a microwave oven, a microwave energy generating means is provided for producing from a conventional power supply, such as a 120-volt 60-cycle alternating current power supply, high frequency microwave energy for heating and cooking food placed in an oven portion of the appliance.
It is desirable to provide an air flow for cooling the microwave energy generating means and it is further desirable to provide an air flow through the oven cavity for dissipating moisture and the like produced in the heating and cooking of the food therein. A substantial number of different arrangements for effecting such air flow have been developed in the prior art.
Illustratively, George B. Long, in U.S. Pat. No. 2,860,026, shows a domestic appliance wherein a magnetron tube is cooled by a blower disposed between the tube and an upper opening in the cabinet. The apparatus is further cooled by a fan drawing air in through an inlet at the bottom of the cabinet, as illustrated in FIG. 1 of the patent. In describing the disclosed structure, Long characterizes the air flow as oppositely to that shown in FIG. 1 of his patent.
Louis P. Polries et al., in U.S. Pat. No. 3,127,495, show a microwave oven having an air flow from an inlet over a microwave generating apparatus in the lower portion of the cabinet and upwardly therefrom through a vertical duct through the cooking space to a front outlet.
In U.S. Pat. No. 3,281,568, Duane B. Haagensen shows an oven control system wherein the cabinet is provided with inlet openings in a front portion thereof and exhaust louvers in the top of the cabinet. The air is moved through the cabinet by means of an exhaust fan with the metallic walls of the oven cavity being cooled by the air circulating over them. A portion of the air stream drawn through the inlet is channeled by a deflector plate into an air pump with the interior of the oven being ventilated by air forced down into the oven cavity by the air pump. The air in the cavity exits through an exhaust duct venting the exhaust air to the exhaust fan.
In U.S. Pat. No. 3,308,261 of Leonard Velander, a microwave oven construction is shown having a plurality of ducts including a first duct connected at one end to a source of pressurized air and at the other end to the exterior of the oven. A second duct provides communication between the cooking cavity and the first duct for aspirating air from the cooking cavity. The device utilizes a single blower for cooling the magnetron and aspirating air from the cooking cavity.
Egbert M. Tingley, in U.S. Pat. No. 3,430,023, shows a microwave oven wherein air is forced into the oven cavity and vented through a series of outlet perforations formed along the front edge of the upper wall of the oven liner.
In U.S. Pat. No. 3,576,417, Egbert M. Tingley shows an electronic oven appliance wherein a blower draws air through a group of louvers at the rear of the cover and passes the air over the electronic components for cooling the same. The air is then exhausted from the component area through perforations is the component tray and through a plastic cover attached to the underside of the component tray from which it enters the oven cavity through an opening in the rear of the plastic cover. From the oven cavity, the air then exits through a group of spaced perforations in the front door of the appliance.
Wallace R. Javes et al., in U.S. Pat. No. 3,654,417, show a microwave oven having an air flow system including a blower for providing heated air flow with one portion thereof being directed into the cavity by suitable duct means. A filter is located on the air exhaust of the cavity for collecting condensation. Another portion of the heated air flow is directed outwardly from the cabinet.
Masataka Suzuki et al. show, in U.S. Pat. No. 3,681,557, a microwave oven wherein cooling air is flowed against the magnetron with the thusly heated air being directed as a hot air air flow directly onto and generally parallel with a major inner surface of the inspection window of the apparatus. This air flow then flows through and across the cooking compartment. The air is then exhausted through a rear, downwardly directed outlet of the cabinet.
Ryumi Igarashi discloses, in U.S. Pat. No. 3,829,649, a microwave oven having a baffle plate in the upper portion of the oven cavity. A fan is provided for cooling the oscillator and circulating air through the cooking chamber with the air entering through a bottom wall of the cabinet and being directed downwardly from the top of the cabinet into the cooking chamber portion of the oven.
In U.S. Pat. No. 3,878,350 of Yutaka Takagi, a microwave oven is shown having an air inlet at the bottom of the cabinet and an air inlet at the top of the cabinet with a fan at the rear of the cabinet discharging the air through an outlet in the rear wall. A blower is provided for directing a portion of the air outwardly through the oven cavity and outwardly through a rear opening to the rear fan.